Automatic Dependent Surveillance Broadcast (ADS-B): Meaning, Operation, Requirements

Jim Goodrich • Thu Apr 02 2026 • Reading time: 10 min

Automatic Dependent Surveillance-Broadcast is an advanced surveillance technology and the standard surveillance system for the majority of the world's aviation industry. It combines an aircraft's positioning source, aircraft avionics, and a ground infrastructure to create an accurate surveillance interface between aircraft and ATC. ADS-B uses satellite signals to track aircraft movements; it is a performance-based surveillance technology that requires transmitters to broadcast position information. ADS-B Out works by broadcasting, once per second, information about an aircraft's GPS location, altitude, ground speed and other data to ground stations and other aircraft. ADS-B Out is required for aircraft with maximum take-off mass greater than 5700 kg or maximum cruising true air speed greater than 250 knots.

What is ADS-B in aviation?

ADS-B (Automatic Dependent Surveillance Broadcast) is the standard surveillance system for the majority of the world's aviation industry. It is a performance-based surveillance technology. ADS-B uses GPS satellites and other navigation tools.

Automatic Dependent Surveillance-Broadcast (ADS-B) is a cooperative surveillance technology in which an aircraft automatically and periodically broadcasts its position, velocity and identity without prompting from ground stations. These ground stations capture this information and immediately relay it to air-traffic control displays, forming an ADS-B tracking system that gives controllers and pilots the same real-time traffic picture. The data stream itself is the basis for ADS-B In, a service of ADS-B that lets equipped aircraft receive the broadcasts of neighbors and of the ground network, assuring direct communication between users and eliminating the voice delays of traditional radar hand-offs.

What is the purpose of Automatic Dependent Surveillance Broadcast (ADS-B)?

The purpose of ADS-B is to provide a continuous picture of air traffic. ADS-B is a surveillance technique in which an aircraft periodically broadcasts its position, altitude, vector and other precise information without pilot intervention. Dependent utilizes GPS or other navigation systems for precise positioning, so the satellite-based system tracks aircraft in real time and provides three-dimensional tracking. The broadcast transmits data to anyone with the appropriate receiving equipment: air traffic control ground stations, other aircraft, and vehicles. Ground displays position to air traffic controllers, while Traffic Information Service-Broadcast (TIS-B) displays positions of nearby aircraft, boosting situational awareness in the cockpit.

By sharing traffic and weather information directly with pilots, ADS-B improves both the safety and efficiency of flight and forms a future-ready foundation that supports the FAA's Next Generation Air Transportation System. Precise GPS-based surveillance offers more accurate last-known positions of aircraft, so ADS-B improves incident, emergency and search and rescue response. Automatic Dependent Surveillance-Rebroadcast (ADS-R) service ensures interoperability between frequencies, extending surveillance coverage offshore and to remote areas where ground stations are absent. Ground staff, family and friends can also track aircraft through freely available software, making identification of the aircraft involved established at all times.

How does ADS-B work in aviation?

ADS-B works by continuously broadcasting the aircraft position. Once each half-second, the aircraft's WAAS-enhanced GPS position is broadcast to the ground and ground stations capture this information and share it with air traffic controllers, who receive the aircraft's GPS location, ground speed, and other data.

The entire process relies on two datalinks. For most airliners and high-altitude traffic, the 1090 MHz Extended Squitter (ES) link is used. 1090ES is based on 1090 MHz, just like older Mode A/C transponders, but the 1090ES transponder is a Mode S transponder with Extended Squitter capability that can be upgraded by retrofitting WAAS GPS and newer software. For lower-flying aircraft in the United States, the system can instead employ the 978 MHz Universal Access Transceiver (UAT). UAT operates at 978 MHz and, besides position, it provides weather and traffic services. Within a 30 nm (55.56 km) diameter around the transmitting aircraft and within 3,500 ft (1,066.8 m), a customized traffic product is delivered. Single-band receivers that listen only to 978 MHz can still pick up air-to-air traffic.

Whichever link is chosen, the same three-dimensional fix - latitude, longitude, and pressure altitude - determines the aircraft's position and is periodically broadcast so that both the ground network and nearby aircraft stay continuously informed.

ADS-B relies on onboard navigation/GPS systems. A Trig transponder typically combined with a GPS transmits highly accurate positional information to ground controllers and directly to other aircraft.

What data does an ADS-B Out equipped aircraft transmit?

ADS B Out broadcasts data like aircraft identification, current position, altitude and velocity through an onboard transmitter once per second. The minimum set of data parameters includes aircraft identification, altitude, velocity, airborne horizontal position - latitude and longitude, surface horizontal position - latitude and longitude, Special Position Identification (SPI), and emergency status. The broadcast carries flight number and callsign, but not airplane type.

My aircraft mechanically broadcasts its call sign and the unique ICAO 24-bit code that identifies my particular aircraft to air traffic authority and to different aircraft. Endlessly, my GPS-derived situation latitude, longitude and precise elevation are transmitted, together with straight speed and level speed. The network transmits information showing whether I am on an airfield ground or in the atmosphere, and the name indicator associates the digital identity to the particular flight schedule.
Jim Goodrich
Pilot, Airplane Broker and Founder of Tsunami Air

What are the components of an ADS-B system?

The components of an ADS-B system are listed below.

ADS-B Out: This is the transmitting portion of the system. Aircraft equipped with ADS-B Out broadcast their precise location, altitude, speed, identification, and other information approximately once per second. This transmission can be received by ground stations and other aircraft equipped with ADS-B In.
ADS-B In: This is the receiving component of the system. Aircraft with ADS-B In capability can receive transmissions from other ADS-B Out equipped aircraft as well as additional flight information services and traffic information from ground stations.

The process begins with the aircraft's avionics determining its precise position using GPS. This information, along with other data like aircraft identification, altitude, speed, and climb/descent rates, is compiled into a digital message. This message is then broadcast on either 1090 MHz (internationally) or 978 MHz (UAT, used in the United States for aircraft flying below 18,000 feet).

What are the services in ADS-B in aviation?

There are two services in ADS-B: ADS-B Out and ADS-B In. There are two datalink technologies: 1090 MHz ES and 978 MHz UAT. The 1090 MHz Mode S transponder with Extended Squitter operates on 1090 MHz. The 978 MHz Universal Access Transceiver operates on 978 MHz. These two paths - 978UAT or 1090ES - give operators a choice for compliance.

What are the ADS-B requirements for aircraft?

Most international ADS-B requirements mandate 1090 MHz ADS-B equipment. Europe requires 1090ES for IFR aircraft with a MTOW exceeding 12,566 pounds (5,700 kg) or maximum cruise airspeed faster than 250 KTAS (463 km/h). Australia requires 1090ES for all IFR operations whereas Hong Kong requires aircraft operating at and above FL180 or receiving ADS-B services outside the United States to carry a Mode-S transponder-based ADS-B transmitter. China stipulates that aircraft flying within ADS-B control airspace must be installed with equipment meeting standards equivalent to or above ES Version 0 (RTCA-260).

ADS-B Out equipment must meet the Minimum Operational Performance Standards for 1090 MHz Extended Squitter as defined in RTCA DO-260B, DO-260C, or Change 1. The 1090ES system must satisfy TSO-C166b performance requirements. Countries that employ space-based ADS-B require 1090ES with antenna diversity - transponder antennas on both the belly and top of the aircraft. For aircraft not operating in 1090ES airspace, UAT operating at 978 MHz is permitted in some areas, and UAT equipment must meet the performance requirements of TSO-C154c.

Are all aircraft required to have ADS-B?

Not all aircraft are required to have ADS-B. All flights within Thailand's airspace require ADS-B, while Australia mandates 1090ES equipment for every IFR operation. Exempted aircraft include gliders, balloons and aircraft without electrical systems; for these, TABS devices are approved. In Canadian airspace, Nav Canada will use the Aireon space-based ADS-B system. Aircraft fall under specific ADS-B aircraft category codes: A5 denotes Heavy (> 300,000 lbs), A6 denotes High performance (> 5g acceleration and 400 kts), B1 is Glider / sailplane, B2 is Lighter-than-air, B4 certifies Ultralight / hang-glider / paraglider (an ultralight vehicle meeting 14 CFR 103.1), B6 defines Unmanned aerial vehicle, and B7 covers Space / trans-atmospheric vehicle. Light sport aircraft do not use the ultralight emitter category unless they meet 14 CFR 103.1.

When does an aircraft need ADS-B Out?

In the continental United States ADS-B Out has been required since January 2, 2020, for all flights in Class A, B, and C airspaces, above 10,000 feet MSL (3,048 meters), and within the 30-nautical-mile (55.56 kilometers) Mode C veil surrounding Class B primary airports. The mandate also covers designated Class E airspace above 10,000 feet MSL (3,048 meters) and certain Class E airspace over the Gulf of Mexico at or above 3,000 feet MSL (914.4 meters) within 12 NM (22.224 kilometers) of the coastline. Guam and the Northern Mariana Islands impose the requirement only at or above FL180 and when operating within 12 NM of the coastline.

Canada now demands ADS-B Out in most controlled airspace, while Europe set a retrofit-compliance deadline of June 7, 2023. Mexico postponed its 1090 ES mandate to January 1, 2022, and sections of Australian Class C airspace between FL145 and FL195 will be phased in after 2027.

ADS-B Out is necessary for operating within high-traffic airspace. Permission immediately into Class B airspace depends on prompt, accurate data about my location and elevation. When I came up to Class B airspace, the regulator gave data that permitted immediate routing.
Jim Goodrich
Pilot, Airplane Broker and Founder of Tsunami Air

Do military aircraft broadcast ADS-B?

Military aircraft routinely broadcast their ADS-B data, yet every sortie begins with a choice: transmit in the open or go dark. FAA permits ADS-B Off for military flights, and the Pentagon is well aware that potential adversaries monitor the public feed. When being easily tracked will run counter to objectives, crews simply select the OFF position.

Participation rates vary by platform and mission. Most large transports and tankers appear as TIS-B targets on ADS-In-equipped civil aircraft, but C-130s usually do not broadcast - maybe 25% do - while helicopter training flights rarely transmit, probably <10%. Fighters, bombers, and special-mission aircraft like the B-2, already difficult to detect on radar, keep their transponders in classified Modes 1, 2, and 4 that cannot be emitted in a blanket broadcast.

To keep the option of silence from becoming a loophole, the Senate moved quickly to close language that allows Department of Defense aircraft to fly without broadcasting their locations, even as public sites like ADS-B Exchange occasionally log a V-22 Osprey or reveal a Black Hawk whose system was not broadcasting at the time of an incident.

Inside the cockpit, ForeFlight's status menu will declare ‘ADS-B Out’ together with any fault codes when a portable receiver like Stratus or Sentry is connected. Garmin Pilot paired with a GDL52 provides the same diagnostic read-out. If paperwork is preferred, the Pilot Operating Handbook and the installation documents list the exact annunciations that signal device failure or loss of GPS input to the ADS-B unit.

Expert behind this article

Jim Goodrich

Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.